This invention relates to dopamine receptors from mammalian species and the corresponding genes. In particular, it relates to the isolation, sequencing and/or cloning of D2 dopamine receptor genes, the synthesis of D2 dopamine receptors by transformed cells, and the manufacture and use of a variety of novel products enabled by the identification and cloning of DNA encoding dopamine receptors.
Dopamine receptors in general have been implicated in a large number of neurological and other disorders, including, for example, movement disorders, schizophrenia, drug addiction, Parkinson""s disease, Tourette syndrome, Tardive Dyskinesia, and many others. As a result, the dopamine receptor has been the subject of numerous pharmacological and biochemical studies.
In general, dopamine receptors can be classified into D1 and D2 subtypes based on pharmacological and biochemical characteristics (1,2). The D2 dopamine receptor has been implicated in the pathophysiology and treatment of the mentioned disorders. In addition, it is known that the D2 dopamine receptor interacts with guanine nucleotide binding proteins to modulate second messenger systems (6,7).
Despite the heavy emphasis placed on elucidation of the existence and properties of the dopamine receptor and its gene, identification, isolation and cloning have been inaccessible heretofore. This is true despite the knowledge that other members of the family of receptors that are coupled to G proteins share a significant similarity in primary amino acid sequence and exhibit an archetypical topology predicted to consist of seven putative transmembrane domains (8). Regarding the serotonin receptor, e.g., see Julius et al., Science, Vol. 241, 558 (1988).
This invention has successfully identified, isolated and cloned mammalian, including human, D2 dopamine receptor gene sequences and produced the encoded dopamine receptor. The corresponding polypeptide has been synthesized. Sequences of both the gene and the polypeptide have been determined. The invention also provides a variety of new and useful nucleic acid, cell line, vector, and polypeptide and medicinal products, inter alia, as well as methods of using these.
Thus, this invention relates to an isolated DNA sequence, an identified portion of which is a structural gene which encodes a polypeptide having the biological activity of a mammalian D2 dopamine receptor. In particular, it relates to an isolated DNA sequence which will hybridize to a DNA sequence encoding a mammalian D2 dopamine receptor. It also relates to fragments, variants and mutants of such sequences, particularly those which also encode a polypeptide having biological activity of a mammalian dopamine receptor, most particularly a mammalian D2 dopamine receptor. In a preferred aspect, the dopamine receptor is human. In another preferred aspect, the sequence is that of rat D2 dopamine receptor as shown in FIG. 1. Of course, the nucleic acids of this invention also include complementary strands of the foregoing, as well as sequences differing therefrom by codon degeneracy and sequences which hybridize with the aforementioned sequences.
In other preferred aspects, this invention includes nucleic acid sequences and fragments useful as oligonucleotide probes, preferably labelled with a detectable moiety such as a radioactive or biotin label. For example, such probes can hybridize with DNA encoding a polypeptide having the biological activity of a D2 dopamine receptor or with DNA associated therewith, e.g., DNA providing control of a D2 dopamine receptor gene or introns thereof, etc. DNA of this invention can also be part of a vector.
The invention also involves cells transformed with vectors of this invention as well as methods of culturing these cells to manufacture polypeptides, e.g., having the biological activity of a D2 dopamine receptor. Preferably, the cells are of mammalian origin when used in such methods.
The invention also relates to polypeptides encoded by the foregoing nucleic acid sequences, especially to isolated mammalian dopamine receptors, preferably of human origin. The invention further relates to polypeptides which are mutants or variants of such receptors, preferably those wherein one or more amino acids are substituted for, inserted into and/or deleted from the receptor, especially those mutants which retain the biological activity of a dopamine receptor. This invention also relates to antibodies, preferably labelled, and most preferably monoclonal, capable of binding a dopamine receptor amino acid sequence, preferably wherein the latter is human, or a fragment of such an antibody.
The invention further relates to compositions comprising one of the various products mentioned above and, typically, a pharmaceutically acceptable carrier as well as to methods of employing these products to achieve a wide variety of utilitarian results.